KR100788105B1 - Planar light source and image display - Google Patents

Abstract

Light is introduced into the light guide plate 43 from the point light source 42. On the surface (pattern surface 61) opposite to the light exit surface 60 of the light guide plate 43, a plurality of deflection patterns 59 having a triangular cross section are provided concave. At the position facing the pattern surface 61 of the light guide plate 43, a prism sheet 44 in which a plurality of arc-shaped prisms 70 is formed is disposed. When the light propagating through the light guide plate 43 is totally reflected in the deflection pattern 59, the light is emitted almost vertically from the light exit surface 60. When light propagating through the light guide plate 43 is obliquely transmitted through the deflection pattern 59, the light is substantially perpendicular to the pattern surface 61 by the prism 70 when passing through the prism sheet 44. Bent in the direction. Such a surface light source device improves the light utilization efficiency. In addition, even in combination with a transmissive display panel, the display device can be less likely to transmit external light or the like.

Surface light source device, image display device

Description

Surface light source device and image display device {PLANAR LIGHT SOURCE AND IMAGE DISPLAY}

The present invention relates to a surface light source device and an image display device of a double-sided light emission type.

1 is a schematic diagram showing the structure of a conventional double-sided display type liquid crystal display device. In this liquid crystal display device 1, the diffusion plates 13 and 14 are disposed on the front and rear surfaces of the liquid crystal display panel 2, respectively, and on the rear side of the liquid crystal display panel 2 via the diffusion plate 14, The backlight 3 which consists of the light source 9 and the light guide plate 10 is arrange | positioned, and the surface side liquid crystal display part 4 is comprised. Further, the diffusion plates 15 and 16 are disposed on the front and rear surfaces of the liquid crystal display panel 5, respectively, and the light source 11 and the light guide plate (back) of the liquid crystal display panel 5 through the diffusion plate 16. The back side 6 liquid crystal display part 7 is formed by arrange | positioning the backlight 6 which consists of 12, and superimposes the front side liquid crystal display part 4 and the back side liquid crystal display part 7 so that the back may face, and both display parts 4 and 7 are shown. The space is partitioned by the double-sided reflecting plate 8. Then, the respective backlights 3 and 6 are turned on so that the liquid crystal display panels 2 and 5 are illuminated from the back side.

However, in such a liquid crystal display device, since it has the structure which arrange | positioned two sets of liquid crystal display parts which consist of a liquid crystal display panel and a backlight, etc., the thickness of a liquid crystal display device becomes thick and this liquid crystal display device There is a problem that a large assembly space is required even in the device to be assembled. In addition, in the case of displaying from both sides, since two backlights must be turned on at the same time, power consumption increases, which is not suitable for a portable device using a rechargeable battery or the like. In addition, since the backlight and the liquid crystal display panel are required on the front and back sides, respectively, the cost is high.

Therefore, it is considered to illuminate the liquid crystal display panels of both front and back with one surface light source device. As such a liquid crystal display device, there is one disclosed in Japanese Patent Laid-Open No. 2002-133906. 2 is a side view of such a liquid crystal display device 21. 3 is a perspective view of the backlight 22 used for this liquid crystal display device 21. In this double-sided light emission type liquid crystal display device 21, liquid crystal display panels 23 and 24 are disposed on both surfaces of the backlight 22, respectively. In the backlight 22, a rod-shaped light source 26 such as a cold cathode tube is disposed on both edges of the light guide plate 25 having a transparent flat plate shape, and the emission light control panel 28 is disposed on both surfaces of the light guide plate 25. This is excreted. A plurality of convex portions 27 having a cylindrical lens shape is formed on an opposing surface of the exiting light control panel 28 with the light guide plate 25, and a central portion of each convex portion 27 is formed of the light guide plate 25. It is in close contact with the surface.

The light emitted from the rod-shaped light source 26 enters the inside of the light guide plate 25 from the edge of the light guide plate 25 to propagate the inside of the light guide plate 25, and the convex portion 27 and the light guide plate 25 are separated from each other. Light incident on the contact surface is incident from the light guide plate 25 to the exiting light control panel 28, totally reflected from the inner surface of the convex portion 27, and exits vertically from the exiting light control panel 28, as shown in FIG. 4. do. Therefore, when the liquid crystal display panel 23 and the liquid crystal display panel 24 are disposed on both surfaces of the backlight 22, the liquid crystal display panels 23 and 24 at the front and back are simultaneously illuminated by one backlight 22. Can be.

However, in such a backlight 22, light vertically incident from the outside, like the light beam A shown in FIG. 4, passes through the light guide plate 25 and the outgoing light control panel 28, and is emitted in the front direction. Therefore, in the case where the transmissive liquid crystal display panel is used as the liquid crystal display panels 23 and 24, when external light enters the other liquid crystal display panel while the liquid crystal display panel is observed, the liquid crystal display panel or the backlight is turned off. The transmitted external light is recognized on the observer side, and there is a problem that the image of the liquid crystal display panel on the back side is reflected or the color unevenness occurs on the image being observed.

An object of the present invention is to provide a surface light source device of a double-sided light emission type having good light utilization efficiency. Moreover, even when it is combined with a transmissive display panel, it is providing the surface-light source device of the double-sided light emission type with little possibility that external light etc. permeate | transmit a display apparatus. In addition, an image display device using the surface light source device is provided.

The surface light source device according to the present invention includes a light source, a light guide plate that confines light from the light source, spreads in a plane shape, and emits light from at least a portion of the light exit surface and the surface opposite to the light exit surface, and an opposite side to the light exit surface. A prism sheet disposed opposite the surface, a deflection pattern for reflecting light propagating through the light guide plate is formed on a surface opposite to the light exit surface of the light guide plate, and from the light exit surface, The reflected light is emitted so that the direction of the peak intensity is directed toward a direction substantially perpendicular to the light exit surface, and from the surface opposite to the light exit surface, the direction of the peak intensity is in a direction perpendicular to the opposite surface. The light is emitted in a direction inclined with respect to the light, and the light emitted from the opposite side has the opposite direction of the peak intensity by the prism sheet. And it is characterized in that which is to deflect toward the surface and the substantially vertical direction.

In the surface light source device of the present invention, the light emitted from the light source enters the light guide plate, and spreads in a plane shape while propagating through the light guide plate. Of the light propagating through the light guide plate, the light incident in the deflection pattern and reflected in the deflection pattern is emitted from the light exit surface with its peak intensity directed toward a direction substantially perpendicular to the light exit surface, and is used as illumination light on the surface side. do. Further, the light emitted from the surface on the side opposite to the light exit surface of the light guide plate so that the direction of the peak intensity is in the inclined direction has a direction in which the direction of the peak intensity is substantially perpendicular to the surface on the opposite side by the prism sheet. It is deflected so as to face, and it exits and becomes illumination light of a back surface side. Therefore, according to this surface light source device, the light emitted from the rear surface side of the light guide plate in the oblique direction and lost can be used as the illumination light by bending in a direction perpendicular to the prism sheet, thereby substantially reducing the front luminance on the surface side. It can be used as a surface light source device of a double-sided light emission type without.

Moreover, in this surface light source device, since the prism sheet is arrange | positioned facing the surface on the opposite side to the light exit surface of a light guide plate, even if external light, such as sunlight or room illumination light, enters perpendicularly from a back surface side, this external light is a prism. The optical path is bent in the sheet, making it difficult to immediately pass through the surface light source device and exit from the surface side. On the contrary, even if external light such as sunlight or indoor illumination light enters vertically from the surface side, the light path is bent in the prism sheet after passing through the light guide plate, so that the surface light source device is immediately transmitted and emitted from the back side. Becomes difficult.

The said light source in embodiment of this invention is a point light source, and the said prism sheet is formed with the pattern of the arc shape centering on the position corresponding to the said point light source. In the case where the light source is a so-called point light source, the pattern of the prism sheet is formed into an arc shape having a center substantially corresponding to a position corresponding to the point light source, so that light is emitted almost over the entire surface on the side opposite to the light exit surface of the light guide plate. The direction of light emitted from the surface opposite the surface can be bent in a direction substantially perpendicular to the opposite surface. In addition, in this invention, a point light source refers to the thing whose size as a whole of the light emitting body inside is 9 mm or less.

In the prism sheet according to another embodiment of the present invention, a cross-sectional triangular pattern is formed, and the one-side right angle on the light source side in the cross section of the pattern is a light source. It is smaller than the one-side right angle on the opposite side to the. As in this embodiment, when the one-side right angle on the light source side is made smaller than the opposite side, and the vertices of the pattern are biased toward the light source side, the light emitted obliquely from the surface opposite to the light exit surface of the light guide plate is effectively prism. It can be transmitted through the sheet and guided in a direction substantially perpendicular to the opposite side thereof.

The said deflection pattern in another embodiment of this invention is formed by the pattern of the cross-sectional outline triangular shape, and the slope of the side of the deflection pattern in the at least some area | region of the surface opposite to the light emission surface of the said light guide plate from the light source side. The inclination angle of is different from the inclination angle of the slope on the side far from the light source of the deflection pattern in another region. In this embodiment, the inclination angles of the slopes on the side far from the light source of the deflection pattern are not all the same, and the amount of light emitted from each area of the surface on the opposite side is adjusted by the difference in the inclination angles.

The deflection pattern according to still another embodiment of the present invention is formed by a cross-sectional roughly triangular pattern in which at least a portion of the slope on the side away from the light source is curved, and at least on the surface opposite to the light exit surface of the light guide plate. The curvature of the slope on the side far from the light source of the deflection pattern in some areas is different from the curvature of the slope on the side far from the light source of the deflection pattern in other areas. In this embodiment, at least a part of the slopes on the side far from the light source of the deflection pattern is curved and the curvatures are not all the same. Is adjusting.

The light source according to still another embodiment of the present invention is a point light source, and the deflection pattern is arranged in an arc shape around the point light source on a surface opposite to the light exit surface of the light guide plate. It features. By setting the light source as the point light source and arranging the deflection pattern in the shape of an arc around the point light source, the light reflected from the point light source and reflected in the deflection pattern is less likely to spread in the circumferential direction of the arc in which the deflection pattern is arranged. Can be.

The image display device of the present invention is characterized by disposing an image display panel facing the light exit surface and the surface on the opposite side to the light exit surface of the surface light source device according to the present invention.

Since the image display device of the present invention can display images on both sides, and furthermore, by using the surface light source device according to the present invention, it is possible to illuminate the image display panels on both sides with one surface light source device. The thickness of the device is difficult to thicken. In addition, the utilization efficiency of light is high, and power consumption is also suppressed. In addition, since external light is difficult to transmit through the surface light source device, when one image display panel is observed, external light incident from the other image display panel does not transmit to the observation side, and the image on the back side is observed. It is possible to prevent the reflection on the side image or the luminance deviation from occurring.

In addition, the component demonstrated above of this invention can be combined arbitrarily as possible.

1 is a schematic side view showing a conventional double-sided display type liquid crystal display device.

Fig. 2 is a schematic side view showing another conventional double-sided display type liquid crystal display device.

3 is a perspective view of a double-sided light emission type surface light source device used in the liquid crystal display device of the same image;

4 is a partially enlarged view for explaining the operation of the surface light source device of the same image.

5 is an exploded perspective view of the surface light source device according to the first embodiment of the present invention.

6 is a schematic cross-sectional view of the surface light source device of the same phase.

7 is a rear view of the light guide plate used for the surface light source device of the same phase;

8 is an enlarged cross-sectional view showing a state in which a point light source is mounted on a light guide plate of the same image;

FIG. 9 is a schematic diagram showing an arrangement of deflection patterns provided in the light guide plate of FIG. 7. FIG.

10A is an enlarged plan view showing a serpentine deflection pattern, and FIG. 10B is a cross-sectional view taken along line X-X of FIG.

11 (a) and 11 (b) are enlarged cross-sectional views illustrating the action of the deflection pattern.

12A is a plan view of a light guide plate provided with a deflection pattern, (b) is an enlarged view of portion A of (a), (c) is an enlarged view of portion B of (a), and (d) is C of (a) Wealth enlarged view.

FIG. 13 is a diagram showing a relationship between a distance from a point light source and a pattern density of a deflection pattern in the light guide plate of the same phase; FIG.

Fig. 14 is a diagram showing the relationship between the distance from a point light source and the pattern length of a deflection pattern in the light guide plate of the same image;

Fig. 15 is a diagram showing the relationship between the distance from a point light source and the pattern number density (number of patterns / area) of the deflection pattern in the light guide plate of the same image;

Fig. 16 is a schematic diagram showing a structure and its function for sending more light to the corner of the light exit surface in the surface light source device of the present invention.

Figure 17 is a schematic view showing a light guide plate filled with a fixed border.

FIG. 18 is a view showing a resin flow when forming a rectangular light guide plate in a rectangular cavity of a mold; FIG.

FIG. 19 is a view for explaining an aspect of forming into a mold having a cavity larger than the target light guide plate and having a swelling resin flow; FIG.

20 is a cross-sectional view of the prism sheet.

Fig. 21 is a diagram explaining the operation of the surface light source device of the present invention.

22A and 22B show comparative examples.

Fig. 23 is a diagram explaining the operation of the surface light source device of the present invention.

FIG. 24 is a diagram showing a directivity characteristic of light emitted from the light guide plate in the comparative example shown in FIG. 22 (b).

Fig. 25 is a diagram showing the directivity characteristic of the illumination light emitted from the surface light source device of the present invention.

FIG. 26A illustrates the behavior of light incident in a deflection pattern when the inclination angle of the re-incidence surface of the light guide plate is wide; FIG. 26B illustrates a deflection pattern in which the inclination angle of the re-incidence surface of the light guide plate is narrow. A diagram showing the behavior of incident light.

FIG. 27A is a cross-sectional view showing a deflection pattern in which the reentrant surface is curved, and (b) is a sectional view showing a deflection pattern in which the reentrant surface is formed in a planar and curved surface.

Fig. 28 is a diagram showing changes in the surface-side luminance rise rate and the back-side luminance rise rate when the inclination angle of the reentrant surface is changed;

Fig. 29 shows changes in the surface-side luminance rise rate and the back-side luminance rise rate when the radius of curvature of the reentrant surface is changed;

30 is a plan view of a surface light source device according to a second embodiment of the present invention.

Fig. 31 is an exploded perspective view of the surface light source device of the same phase;

32 is a schematic diagram showing the structure of a liquid crystal display device according to the present invention.

33 is a perspective view of a mobile phone in a closed state.

Fig. 34 is a perspective view showing the mobile phone in the open state.

Fig. 34 is a perspective view showing the mobile phone in the open state.

<Brief description of the major symbols in the drawings>

DESCRIPTION OF SYMBOLS 41 Surface light source device 42 Point light source 43 Light guide plate 44 Prism sheet 59 Deflection pattern 60 Light exit surface 61 Pattern surface 62 Deflection inclined surface 63 Reentrant surface 70 Prism 81 Liquid crystal display 82 Liquid crystal display panel

Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following examples, and of course, modifications may be made without departing from the spirit of the present invention.

Example 1

FIG. 5 is an exploded perspective view showing the configuration of the surface light source device 41 of the double-sided light emission type according to the first embodiment of the present invention, and FIG. 6 is a schematic sectional view thereof. This surface light source device 41 is comprised by the point light source 42, the light guide plate 43, and the prism sheet 44, The point light source 42 is embedded in the corner of the light guide plate 43, and the prism sheet 44 ) Is disposed to face the rear surface of the light guide plate 43.

The light guide plate 43 is molded into a substantially rectangular flat plate shape by transparent resin or glass with high refractive index, such as polycarbonate resin, an acrylic resin, and methacryl resin. 7 is a rear view of the light guide plate 43. On the back surface of the light guide plate 43, the non-light emitting area 46 is formed around the rectangular surface light emitting area 45 which becomes a substantial surface light source, and the short side of the short side of the light guide plate 43 having a rectangular shape is formed. ), A hole 47 for fitting the point light source 42 is opened outside the surface light emitting area 45 (non-light emitting area 46). The point light source 42 is a resin-molded LED chip, mounted on a film wiring board (FPC) 51 for supplying power to the point light source 42, and inserted into the hole 47 of the light guide plate 43. It is.

8 is a cross-sectional view showing the structure of the point light source 42. The point light source 42 seals the light emitting diode chip 48 in the transparent resin 49 and covers surfaces other than the front surface with the white transparent resin 50. This point light source 42 is mounted on the film wiring board 51 and is fixed by the solder 52. In addition, the film wiring board 51 is fixed to the reinforcement board 53 which consists of glass epoxy resin. The hole L47 for accommodating the point light source 42 penetrates up and down in the corner of the light guide plate 43, and the positioning pin 54 protrudes from the lower surface of the light guide plate 43 in the vicinity thereof. It is. On the other hand, passage holes L55 and 56 through which the positioning pins 54 pass are opened in the film wiring board 51 and the reinforcement plate 53.

Then, an ultraviolet curable adhesive (may be a thermosetting adhesive) 57 is applied to the lower surface of the light guide plate 43 around the base of the positioning pin 54, and the positioning pin 54 is applied. Pass the through-holes L55 and 56 of the film wiring board 51 and the reinforcing plate 53, and position the center of the light guide plate 43 and the light emitting center of the point light source 42 with a CCD camera or the like. After curing, the ultraviolet curable adhesive 57 is cured by irradiating with ultraviolet rays to bond the light guide plate 43 and the point light source 42, and the positioning pin 54 is thermally caulked to the reinforcing plate 53. do.

At this time, as shown in FIG. 8, the point light source is formed by the projections 58 provided on the inner surface of the hole 47 of the light guide plate 43 (either the back side, the front side, or both thereof) of the point light source 42. The centering of (42) may be performed. Although not shown, the light guide plate is used by using a jig with a step for positioning the top surface of the light guide plate 43 and the top surface of the point light source 42 with the light guide plate 43 and the point light source 42 upside down. The center of the 43 and the center of the point light source 42 may be positioned.

In addition, a glass epoxy wiring board or a lead frame may be used instead of the film wiring board 51. In the case where two or more light emitting diode chips are used, a plurality of light emitting diode chips may be concentrated in one place to make point light sources. The point light source 42 may be formed by insert molding a light emitting diode chip directly into the light guide plate 43, or may be disposed outside the light guide plate 43 (a position facing the outer circumferential surface of the light guide plate 43). .

As illustrated in FIG. 9, in the surface light emitting area 45 on the rear surface of the light guide plate 43, a deflection pattern 59 having a plurality or triangular prism shapes is concave in a concentric shape around the point light source 42. It is prepared. The distance between each deflection pattern 59 is relatively wide on the side close to the point light source 42, and gradually shortens as it is separated from the point light source 42. Thus, the surface of the light guide plate 43 (hereinafter referred to as light emission) The brightness | luminance in the surface 60 and back surface (henceforth a pattern surface 61) is made uniform. Hereinafter, this deflection pattern 59 will be described in detail.

(A) and (b) are a plan view and an enlarged cross-sectional view showing the shape of the deflection pattern 59. The said deflection pattern 59 has a substantially uniform cross section in the longitudinal direction, and is arrange | positioned so that the longitudinal direction may become substantially perpendicular to the direction connected with the point light source 42. As shown in FIG. The deflection pattern 59 used in the first embodiment is slightly twisted as shown in Fig. 10 (a). Each deflection pattern 59 is composed of a deflection inclined surface 62 located on the point light source side and a reentrant surface 63 located on a side far from the point light source 42, as shown in FIG. The deflection inclined surface 62 and the reincidence surface 63 are formed in a substantially cross-sectional triangular shape. The inclination angle γ of the deflection inclined surface 62 and the inclination angle δ of the reentrant surface 63 are

γ <δ

γ = 45 ° to 65 °

δ = 80 ° to 90 °

It is preferable to set it as. In particular, the inclination angle γ of the deflection inclined surface 62 is preferably set to approximately 50 °.

When light emitted from the point light source 42 passes through the inner wall surface of the hole 47 and enters the light guide plate 43, the light incident on the light guide plate 43 is the surface of the light guide plate 43 (light exit surface). By repeating total reflection on the back surface 60 and the pattern surface 61, the light guide plate 43 propagates through the inside of the light guide plate 43 and spreads to the entire surface light emitting region 45 of the light guide plate 43. Light incident from below on the deflection inclined surface 62 of the deflection pattern 59 is totally reflected toward the light exit surface 60 by the deflection inclined surface 62 as shown in FIG. 11 (a). , The light exits from the light exit plane 60 so that the direction of the maximum light intensity is directed in a direction substantially perpendicular to the light exit plane 60. In addition, the light incident from the upward direction on the deflection inclined surface 62 of the deflection pattern 59 during the first half passes through the deflection inclined surface 62 as shown in FIG. 11 (b), and the direction of the maximum light intensity is patterned. It exits from the pattern surface 61 so that it may face the direction obliquely inclined with respect to the surface 61. As shown in FIG. Therefore, the direction of the light beam propagating through the inside of the light guide plate 43 and the direction of the light emitted from the light exit surface 60 and the pattern surface 61 are horizontal when viewed from the direction perpendicular to the light exit surface 60. In the direction (direction along the circumference with respect to the point light source 42), it does not scatter so much but progresses substantially radially centering on the point light source 42. As shown in FIG.

(A) (b) (c) (d) shows the method of arrangement | positioning the whole deflection pattern 59, and FIG. 13 shows the change of the pattern density (area ratio) of the deflection pattern 59 in a radial direction. 14 shows a change in the pattern length, and FIG. 15 shows a change in the number of patterns per unit area. Here, r represents the distance from the point light source 42. As shown in FIG. 13, the deflection pattern 59 has a larger density as the distance r from the point light source 42 increases. This is for making the luminance of the light output surface 60 and the pattern surface 61 uniform. As a method of gradually increasing the deflection pattern density, it is also possible to gradually increase the number of deflection patterns per unit area, but in Example 1, the light guide plate 43 is arranged in a plurality of annular bands according to the distance from the point light source 42. ) The shape is divided into one zone, and in each zone, as shown in FIG. 15, the number of deflection patterns per unit area is constant, and the number of deflection patterns per unit area is increased in step shapes for each zone, and As shown in the figure, the length of the deflection pattern is gradually changed in each zone. At the boundary of the zone, the pattern length is shortened once.

(B) (c) (d) has shown the deflection pattern 59 in the location of A, B, and C of FIG. 12 (a), respectively. 12 (b) shows that the pitch in the radial direction and the pitch in the circumferential direction of the deflection pattern 59 are 140 μm in the region A closest to the point light source 42. The pattern 59 and the outer deflection pattern 59 do not overlap in the radial direction. 12 (c) shows the intermediate region B, which has a pitch in the radial direction of the deflection pattern 59 and a pitch in the circumferential direction as well as 70 μm, and shows an inner deflection pattern 59 and an outer side. The deflection patterns 59 overlap each other. 12 (d) shows an area c far from the point light source 42, in which the pitch in the radial direction is 35 μm and the pitch in the circumferential direction is 140 μm. 12 (b) (c) and (d) show a deflection pattern extending in a straight line shape, the serpentine deflection pattern 59 as shown in FIG. 10 is shown in FIG. 12 (b) (c) (d). ) May be arranged.

In addition, while the long side of the light guide plate on the opposite side to the stage where the point light source 42 is disposed is formed straight, the long side of the light guide plate on the side close to the point light source 42 is one step or a plurality. But it is cut obliquely. Similarly, the short side is also formed obliquely in the vicinity of the point light source 42. When the slopes 64 and 65 are provided on the long side and the short side close to the point light source 42, as shown in FIG. 16, a part of the light emitted from the point light source 42 is the slope side 64 of the long side. The total reflection at the slope portion 65 on the side and the short side allows light to be sent to the corner of the light guide plate 43 (area drawn in FIG. 16). When the point light source 42 is placed at the corner of the light guide plate 43, other corners are likely to be dark, but according to such a structure, the light totally reflected by the slope 64 and the slope 65 is the surface of the light guide plate 43. By sending to the corner of the light emission area 45, the luminance distribution of the light emission surface 60 and the pattern surface 61 can be made more uniform, and the efficiency of the surface light source device 41 can be improved.

In addition, in the case where the fixed edge 66 is attached to the light guide plate 43 as shown in FIG. 17, the light guide plate 43 is formed when the slopes 64 and 65 and the fixed edge 66 for reflecting light are in close contact with each other. It is easy to produce a flaw etc. in the inclined part 64 and 65, and there exists a possibility that a reflection characteristic may be impaired. In order to prevent this, a small convex small protrusion 67 is provided at a part of or near the slope portions 64 and 65 for light reflection use, and the light guide plate 43 is fixed with the convex small protrusion 67. ) And a gap is formed between the slopes 64 and 65 and the fixed edge 66.

When resin molding the light guide plate 43 having a rectangular shape as described above, if the rectangular light guide plate 43 is to be molded directly, as shown in FIG. 18, the resin in the mold 68 The flow becomes uneven, and it is difficult to achieve uniform pattern transferability over the entire surface, and warpage tends to occur in the light guide plate 43. However, as shown in Fig. 19, a mold 68 larger than the light guide plate 43 intended to be manufactured is made, and a large light guide plate 69 having a fan shape or a semi-circular shape is produced by using the mold 68, and this is appropriately cut. The light guide plate 43 can be formed by this. Thus, when the large light guide plate 69 with good resin fluidity is molded and the desired light guide plate 43 is produced by cutting this, the flow of resin is uniform in any direction during molding of the large light guide plate 69. As a result, uniform pattern transferability can be achieved on the entire surface, and warpage is less likely to occur in the light guide plate 43.

Referring to the dimensions of the surface light source device 41 shown in FIG. 5, the length of the light guide plate 43 in the short side direction is 33 mm and the length in the long side direction is about 43 mm (including the light source attachment portion, about 47 mm). , The thickness is 0.1 mm. The width of the non-light emitting region 46 of the light guide plate 43 is 0.2 mm. The light emitting diode, which is the point light source 42, has a width of about 25 mm and a length of 1.3 mm.

Prism sheet 44 is shown in FIG. 5. 20 is a sectional view of the prism sheet 44. A plurality of prisms 70 having an arc shape are formed on the upper surface of the prism sheet 44, and each prism 70 is formed in an arc shape centering on a position corresponding to the point light source 42. Each prism 70 has a triangular cross section, and its peak is inclined toward the point light source. That is, as shown in FIG. 20, when the one-sided right angle on the side close to the point light source 42 of the prism 70 is α, and the one-sided right angle on the opposite side is β, α = 10 ° to 40 ° and β = 25 It is set to ° -55 degrees ((alpha) <(beta)). Further, if the pitch of the prism is p, the thickness of the prism sheet 44 is t, and the height of the prism 70 is h, the pitch p = 30 m, the thickness t = 100 to 500 m, the height h ) = 18 to 32 nm. The prism sheet 44 may be molded by the transparent resin as a whole, or the prism 70 made of the transparent resin may be molded on the glass substrate.

Next, the effect of the surface light source device 41 according to the present invention will be described. 21 is a schematic view for explaining the operation of the surface light source device 41. The light emitted from the point light source 42 enters the light guide plate 43 from the light incident surface of the light guide plate 43, and the surface (light exit surface 60) and the back surface of the light guide plate 43 (pattern surface ( 61)) is propagated while repeating total reflection, and spreads to the entire light guide plate 43. When the light propagating through the light guide plate 43 is incident on the deflection pattern 59 from the back surface side after reflecting from the pattern surface 61 as shown by the broken line arrow in FIG. 21, the light is deflected pattern. By the deflection inclined surface 62 of 59, it is totally reflected toward the direction substantially perpendicular to the light exit surface 60, and is emitted toward the direction substantially perpendicular to the light exit surface 60. FIG. In this way, the light emitted from the entire surface light emitting area 45 of the light exit surface 60 toward the direction perpendicular to the light exit surface 60 becomes the illumination light on the surface side.

In addition, when light propagating through the light guide plate 43 enters the deflection pattern 59 from the surface side, as indicated by the solid arrows in FIG. 21, the deflection inclined surface 62 passes through the pattern surface 61. It exits obliquely toward the inclined direction from the direction of the vertical line set in the). The light emitted obliquely from the pattern surface 61 enters the prism sheet 44, is refracted and deflected by the prism 70, and is emitted toward a direction substantially perpendicular to the pattern surface 61. In this way, the light emitted from the entire surface light emitting area 45 of the pattern surface 61 toward the direction perpendicular to the pattern surface 61 becomes the illumination light on the back surface side. Therefore, according to the surface light source device 41 of the present invention, the illumination light can be emitted in a planar shape from both front and back sides of the light guide plate 43 toward the front side and front side directions of the light guide plate 43, and the surface light source of double-sided light emission type. It can be used as.

Here, the cross-sectional shape of the prism 70 provided in the prism sheet 44 is asymmetrical, and the one-side right angle α on the side close to the point light source 42 is smaller than the one-side right angle β on the opposite side ( 20), the light emitted from the pattern surface 61 is inclined obliquely in a direction away from the point light source 42 as it goes outwardly perpendicular to the pattern surface 61 of the light guide plate 43. 44 is a shape suitable for changing the angle in the direction perpendicular to the pattern surface 61.

FIG. 22A shows the point light source 42, the light guide plate 43, and the direction of light emitted from the light guide plate 43. The point light source 42 and the light guide plate 43 (the one in which the prism sheet 44 does not exist) as used in Example 1 may also be used as a single-side light-emitting backlight. In that case, the light emitted from the light exit surface 60 of the light guide plate 43 becomes the illumination light, and the light obliquely exited from the pattern surface 61 becomes the lost light. In order to prevent that from happening, in the case of a single-side light-emitting backlight, as shown in Fig. 22B, a reflecting plate 71 is provided to face the pattern surface 61, and it is oblique from the pattern surface 61. Reflected light is reflected by the reflecting plate 71 and reincident into the light guide plate 43, and is emitted to the surface side.

In the double-sided light emission type surface light source device 41 of the present invention, since the light which has been lost as described above is refracted by the prism sheet 44, the double-sided light emission is enabled as the illumination light on the back side. Compared with the case of the single-side light emission type, the back side light emission can be enabled without substantially decreasing the front luminance on the surface side, and a double-side light emission type surface light source device with high light utilization efficiency can be produced.

In addition, in the surface light source device 41 of the present invention, as shown in FIG. 23, even if external light enters vertically from the surface side, the external light transmitted vertically through the light guide plate 43 is caused by the prism sheet 44. Since the output direction is bent at an angle, it is difficult for external light to be emitted from the back side in the observation direction (front side). In addition, even when external light enters vertically from the back surface side, since the external light is bent obliquely by the prism sheet 44 and enters the light guide plate 43, it is difficult for external light to be emitted in the observation direction (front side) even on the surface side. Lose. Therefore, as described later, even when a transmissive liquid crystal display panel is disposed on both front and back sides of the surface light source device 41 and used as a double-sided display type liquid crystal display device, luminance deviation is less likely to occur on both surfaces. For example, when the image of the liquid crystal display panel on the front side is observed, when external light enters from the back side and is transmitted to the surface side, the image of the liquid crystal display panel on the back side is seen from the surface side or the external light from the surface side. If this is seen, luminance deviation etc. may arise in the image observed, and there exists a possibility that the quality of an image may fall. However, in the surface light source device 41 of the present invention, even in such a case, since external light incident from the back surface side does not transmit to the surface side, an image on the back side is reflected on the surface side, or external light is visible from the surface side. The quality of a liquid crystal display device can be improved without doing. The same applies to the case where external light is incident vertically from the front side when the image on the back side is observed.

FIG. 24 shows the illumination light totally reflected by the deflection pattern 59 and emitted from the light exit surface 60 in the comparative example in which the reflecting plate 71 is disposed on the rear surface side of the light guide plate 43 as shown in FIG. 22 (b). Lossy light emitted from the pattern surface 61 at an angle and reflected from the reflecting plate 71 and emitted from the light exit surface 60 (or loss light emitted from the pattern surface 61 in FIG. 22A). Each of the directivity characteristics and the sum of both, the vertical axis represents the light intensity (arbitrary unit) of the emitted light, and the horizontal axis represents the emission angle of the emitted light based on the vertical line of the light exit surface 60. In the light guide plate 43 used here, the reincident surface 63 of the deflection pattern 59 is comprised by the plane and the curved surface (refer FIG. 27 (b)), and the inclination angle of the deflection inclination surface 62 is (gamma) = 50 degrees. The inclination angle of the planar portion of the reentrant surface 63 is δ = 80 ° and the radius of curvature of the curved portion is R = 1.5 μm. As can be seen from the directivity characteristic of FIG. 24, the lost light has a large light intensity in a direction inclined at about 30 ° to 90 ° with respect to the vertical line of the light exit surface 60, and does not contribute to the front brightness. Do not.

FIG. 25 shows the illumination light on the front side emitted from the light exit surface 60 and the illumination light on the back side emitted from the pattern surface 61 and transmitted through the prism sheet 44 in the surface light source device 41 of the present invention. A diagram showing the sum of the respective directing characteristics and the sum of the two, wherein the vertical axis represents the light intensity (arbitrary unit) of the emitted light, and the horizontal axis is based on the vertical line of the light exit plane 60 or the vertical line of the pattern plane 61. The exit angle of the exit light is shown. The light guide plate 43 used here is the same as that used for the measurement of FIG. In addition, the prism sheet 44 used here has the thickness t = 125 micrometers, the pitch of the prism 70 p = 30 micrometers, the height h = 32 micrometers, and the inclination (alpha) = 20 degrees (the side near a point light source) ), β = 30 ° (side far from the point light source). Comparing this directivity characteristic with the directivity characteristic of FIG. 24, the front luminance on the front side is almost equivalent to the illumination luminance of the illumination light of FIG. 24, and furthermore, the lost light of FIG. 24 is eliminated to become the front luminance of the illumination light on the back side. I can see that there is. Therefore, even if the characteristics of the total outgoing light (illumination light and the lost light) shown in FIG. 24 and the characteristics of the total outgoing light (surface and backside outgoing) shown in FIG. 25 are compared, according to the present invention, It can be seen that the emitted light is concentrated on the front side, and the light utilization efficiency is improved.

Next, the cross-sectional shape of the deflection pattern 59 of the light guide plate 43 will be described. 26A and 26B show a deflection pattern 59 having a triangular cross section. The inclination angle γ of the deflection inclined surface 62 is determined to totally reflect the light and to emit it in a direction perpendicular to the light exit surface 60. On the other hand, when the inclination angle δ of the reentrant surface 63 is increased, as shown in FIG. 26 (b), a part of the light incident on the deflection inclined surface 62 and transmitted through the deflection inclined surface 62 is reentrant surface ( When the light is reincident from the light guide plate 43 to the light guide plate 43, the amount of light emitted from the pattern surface 61 toward the back surface side can be reduced, and the inclination angle δ of the reincident surface 63 is reduced. As shown in FIG. 6, light incident on the deflection inclined surface 62 and transmitted through the deflection inclined surface 62 is less likely to be captured by the reentrant surface 63, thereby increasing the amount of light emitted from the pattern surface 61 toward the back surface side. . Therefore, by changing the inclination angle γ of the deflection inclined surface 62 of the deflection pattern 59 for each region of the pattern surface 61 on the back surface of the light guide plate 43, the amount of light emitted from the region can be increased or decreased. For example, it can adjust so that the quantity of light radiate | emitted to the back surface side in the whole surface emitting area 45 may be uniform.

In addition, in order to adjust the amount of light emitted from the deflection pattern 59, in addition to adjusting the angle δ of the reentrant surface 63, as shown in Fig. 27A, the reentrant surface 63 is curved to the curved surface. You may form by. In addition, the amount of light emitted from the deflection pattern 59 can be adjusted by changing the curvature or the radius of curvature R. FIG. Further, as shown in Fig. 27B, the reentrant surface 63 may be formed by a plane and a curved surface. In this case, since the amount of emitted light can be changed by the inclination angle δ of the planar portion and the radius of curvature R of the curved portion, the design parameter is increased and more delicate design is possible.

FIG. 28 is a surface (light exit surface) when the inclination angle δ of the reentrant surface 63 is changed in the deflection pattern 59 having a cross-sectional triangle shape as shown in FIGS. 26A and 26B. (60) shows the result of measuring the luminance increase rate on the side and the luminance rise rate on the back surface (pattern surface 61) side, and the vertical axis represents the relative luminance of the emitted light, and the horizontal axis represents the inclination angle δ of the reincident surface 63. Indicates. However, the luminance (rising rate) is based on the value when the inclination angle of the reentrant surface 63 is δ = 80 °. According to Fig. 28, the surface-side luminance increase rate is hardly changed by the inclination angle δ of the reentrant surface 63, but in the region where the inclination angle δ is less than 60 °, the back surface is reduced as the inclination angle δ becomes smaller. The relative luminance at the side is increasing, which coincides with the result of FIG.

FIG. 29 shows the rate of increase in luminance of the surface (light exit surface 60) side when the curvature radius R of the reentrant surface 63 is changed in the deflection pattern 59 as shown in FIG. 27 (a). The result of measuring the luminance increase rate on the back and back surfaces (pattern surface 61) is shown, and the vertical axis represents the relative luminance of the emitted light, and the horizontal axis represents the radius of curvature R of the reincident surface 63. However, the luminance (rising rate) is based on the value when the radius of curvature of the reentrant surface 63 is R = 1.5 m. According to Fig. 29, the surface-side luminance increase rate is hardly changed by the radius of curvature R of the reentrant surface 63, but in the region where the radius of curvature R is 4 µm or more, as the radius of curvature R increases, Relative luminance is increasing.

In the above embodiment, the surface light source device of a double-sided light emission type using a so-called point light source using a light emitting diode has been described, but the present invention can also be applied to a surface light source device using a rod-shaped light source such as a cold cathode tube. In this case, however, the pattern of the prism sheet also needs a design change as appropriate, such as using a linear parallel pattern in accordance with the shape of the light source.

Example 2

30 is a plan view showing the surface light source device 72 according to the second embodiment of the present invention, and FIG. 31 is an exploded perspective view thereof. In the surface light source device 72 according to the second embodiment, a plurality of point light sources 42 are disposed to face the central portion at the side of the short side of the light guide plate 43. In the surface light emitting area 45 on the back surface of the light guide plate 43, a plurality of deflection patterns 59 are formed in an arc shape with the light emitting area of the point light source 42 substantially in the center. As described in the first embodiment, the deflection pattern 59 is formed in a cross-sectional schematic right triangle shape. In addition, the prism surface may be formed in the side surface of the light guide plate 43 facing the point light source 42 in order to increase the spread of the light incident from the point light source 42 into the light guide plate 43. In addition, in Example 2, the prism sheet 44 provided in the lower surface side of the point light source 42 also has the center corresponding to the light emission area | region of the point light source 42 similarly to the deflection pattern 59, An arc-shaped deflection pattern 59 having a cross-sectional triangular shape is arranged in a concentric shape.

In addition, in this invention, a point light source means that the magnitude | size of the whole light emitting body as a whole is 9 mm or less. For example, in the case where there is only one light emitting body (such as a bare chip of a light emitting diode) inside, if the size of the light emitting body is 9 mm or less, the point light source referred to in the present invention can be said. In addition, as shown in FIG. 30, when the several point light source 42 is provided and the light emitting body 73, such as a bare chip of a light emitting diode, is sealed inside each point light source 42, FIG. The width D as a whole of the light emitting body 73 shown in 30 may be 9 mm or less. In connection with this, in Example 2 shown in FIG. 30, the size of the surface light emission area | region 45 on the back surface of the light-guide plate 43 is length L = 40 mm, width W = 30 mm, and width (The width | variety which an external resin also included) arrange | positions two 3 mm point light sources 42 and 3 mm space | interval, and the width of the whole point light source 42 is set to 9 mm.

(Liquid crystal display device)

32 is a schematic side view of the liquid crystal display device 81 using the double-sided light emission type surface light source device 41 having the above structure. In this liquid crystal display device 81, the transmissive liquid crystal display panel 82 is disposed to face the surface (light exit surface 60) of the surface light source device 41 according to the present invention, and to the prism sheet 44. A transmissive liquid crystal display panel 83 is disposed to face each other.

According to such a liquid crystal display device 81, an image is displayed by illuminating the liquid crystal display panel 82 and the liquid crystal display panel 83 on both sides of the front and back by one surface light source device 41 (backlight). Can be. In addition, other images may be displayed on the front and back liquid crystal display panels 82 and 83.

Moreover, in such a liquid crystal display device 81, since the surface light source device 41 is good as one, the thickness of the liquid crystal display device 81 can be made thin. In addition, since the surface light source device 41 of the present invention is used, light utilization efficiency is good. The battery consumption can be suppressed.

In addition, according to the liquid crystal display device 81, as described above, no external light enters from the liquid crystal display panels 82 and 83 on the front side or the back side, and does not pass through the liquid crystal display device 81, Luminance variation is less likely to occur on both surfaces due to external light transmitted through the liquid crystal display device 81.

(Cell Phone)

33 and 34 are perspective views showing the folding cell phone 84, which shows a perspective view of the folded state in FIG. 33 and a perspective view of the open state in FIG. The mobile phone 84 includes a circuit board, a battery, and the like, the main body portion 86 having switches and ten keys 85 provided on the surface thereof, and the display portion 87 provided with a liquid crystal display being rotated by the hinge portion 88. Freely connected. In the display unit 87, a liquid crystal display device 81 as shown in FIG. 32 is incorporated as a liquid crystal display. In the liquid crystal display device 81 used here, the liquid crystal display panel 83 on the back side has a surface. It is smaller than the liquid crystal display panel 82 on the side, and the liquid crystal display panel 82 on the front side is exposed to the inner surface of the display portion 87, and the liquid crystal display panel 83 on the back side of the display portion 87 Exposed to the outside.

According to such a mobile phone 84, since the light utilization efficiency of the surface light source device 41 is high and the power consumption of the liquid crystal display device 81 can be reduced, the battery holding time of the mobile phone 84 is lengthened. The frequency of charge of the battery can be reduced.

In addition, when the mobile phone 84 is opened and the liquid crystal display panel 82 on the inner side is observed, even if external light such as sunlight enters from the liquid crystal display panel 83 on the outside, the incident external light is the inside surface. Since the emission direction is bent obliquely by the prism sheet 44 of the light source device 41, it is difficult to exit from the liquid crystal display panel 82 inside. Therefore, the image of the liquid crystal display panel on the back side is transmitted through the liquid crystal screen being observed, and the luminance deviation or the like is less likely to occur on the screen, and the visibility of both surfaces becomes good.

As described in the above, according to the embodiment, according to the surface light source device of the present invention, the light emitted from the back surface side of the light guide plate in the oblique direction and lost can be bent in the vertical direction with the prism sheet and used as illumination light. It is possible to emit light also from the back side without substantially reducing the front luminance on the front side.

In addition, in the surface light source device of the present invention, even when external light such as sunlight or indoor illumination light enters vertically from the back side from the back side, the external light is bent in the prism sheet so that the surface light source device passes straight through the surface. It is difficult to exit from the side. Conversely, even if external light such as sunlight or room illumination light enters vertically from the back side from the front side, the light path is bent in the prism sheet after passing through the light guide plate, so that the surface light source device passes straight through the surface light source device. It is hard to get out.

According to the surface light source device of the present invention, the light emitted from the rear surface side of the light guide plate in the oblique direction and lost can be used as the illumination light by bending in a direction perpendicular to the prism sheet, thereby substantially decreasing the front luminance on the surface side. It is possible to emit light even from the back side without.

In addition, in the surface light source device of the present invention, even when external light such as sunlight or indoor illumination light enters vertically from the back side from the back side, the external light is bent in the prism sheet so that the surface light source device passes straight through the surface. It is difficult to exit from the side. Conversely, even if external light such as sunlight or room illumination light enters vertically from the back side from the front side, the light path is bent in the prism sheet after passing through the light guide plate, so that the surface light source device passes straight through the surface light source device. It is hard to get out.

Claims (7)

A light guide plate for confining the light source, the light from the light source, spreading in a plane shape, and emitting light from at least a portion of the light exit surface and the surface opposite to the light exit surface; and a prism sheet disposed to face the opposite side of the light exit surface. Has, On the surface opposite to the light exit surface of the light guide plate, a deflection pattern having an inclination angle of 45 ° to 65 ° for reflecting light propagating through the light guide plate is formed, From the light exit surface, the light reflected by the deflection pattern is emitted so that the direction of the peak intensity is directed in the direction perpendicular to the light exit surface, From the surface opposite to the light exit surface, light is emitted so that the direction of the peak intensity is in the direction inclined with respect to the direction perpendicular to the opposite surface, The light emitted from the opposite side is deflected by the prism sheet so that the direction of the peak intensity is directed toward the direction perpendicular to the opposite side. The method of claim 1, The light source is a point light source, and the prism sheet is formed with an arc-shaped pattern centered on a position corresponding to the point light source. The method of claim 1, The prism sheet is formed with a cross-sectional triangular pattern, and the one-side right angle on the light source side in the cross section of the pattern is smaller than the one-side right angle on the opposite side to the light source. The method of claim 1, The deflection pattern is formed by a cross-sectional triangular pattern, wherein the inclination angle of the inclination angle of the slope on the side far from the light source of the deflection pattern in at least a portion of the surface opposite to the light exit surface of the light guide plate is different in the deflection pattern. The surface light source device which is different from the inclination angle of the slope on the side far from a light source. The method of claim 1, The deflection pattern is formed by a cross-sectional triangular pattern in which at least a portion of the slope on the side far from the light source is curved, and is far from the light source of the deflection pattern in at least a portion of the surface opposite to the light exit surface of the light guide plate. The curvature of the side slope is different from the curvature of the side slope far from a light source of the deflection pattern in another area | region. The method of claim 1, The said light source is a point light source, and the said deflection pattern is arrange | positioned in circular arc shape centering on the said point light source in the surface on the opposite side to the light emission surface of the said light guide plate. An image display apparatus is disposed so as to face the light emitting surface and the surface opposite to the light emitting surface of the surface light source device according to any one of claims 1 to 5.

Images